Plant-derived polymers are received attention as alternative resins to petroleum-derived polymers. Attempts have been made to adopt such plant-derived polymers to release liners. The release liners are generally produced by applying a thermally cross-linkable silicone resin onto a release liner substrate surface, and thermally curing the applied silicone resin. Suppose that a poly(lactic acid) film or cellophane, as a film of the plant-derived polymer, is used as a release liner substrate; and the thermally cross-linkable silicone resin is applied thereon and cured under a regular curing condition of 100° C. or higher. In this case, the resulting release liner suffers from deformation such as wrinkling. To prevent this, there have been proposed techniques for applying a thermally cross-linkable silicone resin to any of the plant-derived film substrates.
Typically, Japanese Unexamined Patent Application Publication (JP-A) No. 2003-026837 proposes a technique of using a silicone resin that is curable at a temperature of lower than 100° C. However, thermally cross-linkable silicone resins usable in this technique are limited to specific ones. In addition, the technique needs reduction in amount of a reaction retardant, thereby suffers from inferior pot stability (shorter pot life) of the silicone resin, and requires special coating equipment.
Japanese Patent No. 4200405, Japanese Patent No. 4200406, and Japanese Patent No. 4214254 disclose techniques of using a biaxially stretched poly(lactic acid) film as a release film substrate. These techniques, however, should perform heat setting (heat fixation) in a specific temperature range of from 145° C. to the melting temperature of the poly(lactic acid).